Index of Section 3 Manual Pages
| Interix / SUA | FileSystem.3 | Interix / SUA |
Filesystem(3) Tcl Library Procedures Filesystem(3)
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NAME
Tcl_FSRegister, Tcl_FSUnregister, Tcl_FSData,
Tcl_FSMountsChanged, Tcl_FSGetFileSystemForPath,
Tcl_FSGetPathType, Tcl_FSCopyFile, Tcl_FSCopyDirectory,
Tcl_FSCreateDirectory, Tcl_FSDeleteFile, Tcl_FSRemoveDi-
rectory, Tcl_FSRenameFile, Tcl_FSListVolumes, Tcl_FSEval-
File, Tcl_FSLoadFile, Tcl_FSMatchInDirectory, Tcl_FSLink,
Tcl_FSLstat, Tcl_FSUtime, Tcl_FSFileAttrsGet,
Tcl_FSFileAttrsSet, Tcl_FSFileAttrStrings, Tcl_FSStat,
Tcl_FSAccess, Tcl_FSOpenFileChannel, Tcl_FSGetCwd,
Tcl_FSChdir, Tcl_FSPathSeparator, Tcl_FSJoinPath, Tcl_FSS-
plitPath, Tcl_FSEqualPaths, Tcl_FSGetNormalizedPath,
Tcl_FSJoinToPath, Tcl_FSConvertToPathType, Tcl_FSGetInter-
nalRep, Tcl_FSGetTranslatedPath, Tcl_FSGetTranslated-
StringPath, Tcl_FSNewNativePath, Tcl_FSGetNativePath,
Tcl_FSFileSystemInfo, Tcl_AllocStatBuf - procedures to
interact with any filesystem
SYNOPSIS
#include
int
Tcl_FSRegister(clientData, fsPtr)
int
Tcl_FSUnregister(fsPtr)
ClientData
Tcl_FSData(fsPtr)
void
Tcl_FSMountsChanged(fsPtr)
Tcl_Filesystem*
Tcl_FSGetFileSystemForPath(pathObjPtr)
Tcl_PathType
Tcl_FSGetPathType(pathObjPtr)
int
Tcl_FSCopyFile(srcPathPtr, destPathPtr)
int
Tcl_FSCopyDirectory(srcPathPtr, destPathPtr, errorPtr)
int
Tcl_FSCreateDirectory(pathPtr)
int
Tcl_FSDeleteFile(pathPtr)
int
Tcl_FSRemoveDirectory(pathPtr, int recursive, errorPtr)
int
Tcl_FSRenameFile(srcPathPtr, destPathPtr)
Tcl_Obj*
Tcl_FSListVolumes(void)
int
Tcl_FSEvalFile(interp, pathPtr)
int
Tcl_FSLoadFile(interp, pathPtr, sym1, sym2, proc1Ptr, proc2Ptr, handlePtr, unloadProcPtr)
int
Tcl_FSMatchInDirectory(interp, result, pathPtr, pattern, types)
Tcl_Obj*
Tcl_FSLink(linkNamePtr, toPtr, linkAction)
int
Tcl_FSLstat(pathPtr, statPtr)
int
Tcl_FSUtime(pathPtr, tval)
int
Tcl_FSFileAttrsGet(interp, int index, pathPtr, objPtrRef)
int
Tcl_FSFileAttrsSet(interp, int index, pathPtr, Tcl_Obj *objPtr)
CONST char**
Tcl_FSFileAttrStrings(pathPtr, objPtrRef)
int
Tcl_FSStat(pathPtr, statPtr)
int
Tcl_FSAccess(pathPtr, mode)
Tcl_Channel
Tcl_FSOpenFileChannel(interp, pathPtr, modeString, permissions)
Tcl_Obj*
Tcl_FSGetCwd(interp)
int
Tcl_FSChdir(pathPtr)
Tcl_Obj*
Tcl_FSPathSeparator(pathPtr)
Tcl_Obj*
Tcl_FSJoinPath(listObj, elements)
Tcl_Obj*
Tcl_FSSplitPath(pathPtr, lenPtr)
int
Tcl_FSEqualPaths(firstPtr, secondPtr)
Tcl_Obj*
Tcl_FSGetNormalizedPath(interp, pathPtr)
Tcl_Obj*
Tcl_FSJoinToPath(basePtr, objc, objv)
int
Tcl_FSConvertToPathType(interp, pathPtr)
ClientData
Tcl_FSGetInternalRep(pathPtr, fsPtr)
Tcl_Obj*
Tcl_FSGetTranslatedPath(interp, pathPtr)
CONST char*
Tcl_FSGetTranslatedStringPath(interp, pathPtr)
Tcl_Obj*
Tcl_FSNewNativePath(fsPtr, clientData)
CONST char*
Tcl_FSGetNativePath(pathPtr)
Tcl_Obj*
Tcl_FSFileSystemInfo(pathPtr)
Tcl_StatBuf*
Tcl_AllocStatBuf()
ARGUMENTS
Tcl_Filesystem *fsPtr (in) Points to a structure
containing the
addresses of proce-
dures that can be
called to perform the
various filesystem
operations.
Tcl_Obj *pathPtr (in) The path represented
by this object is used
for the operation in
question. If the
object does not
already have an inter-
nal path representa-
tion, it will be con-
verted to have one.
Tcl_Obj *srcPathPtr(in) As for pathPtr, but
used for the source
file for a copy or
rename operation.
Tcl_Obj *destPathPtr(in) As for pathPtr, but
used for the destina-
tion filename for a
copy or rename opera-
tion.
CONST char *pattern (in) Only files or directo-
ries matching this
pattern will be
returned by
Tcl_FSMatchInDirec-
tory.
GlobTypeData *types (in) Only files or directo-
ries matching the type
descriptions contained
in this structure will
be returned by
Tcl_FSMatchInDirec-
tory. It is very
important that the
'directory' flag is
properly handled.
This parameter may be
NULL.
Tcl_Interp *interp (in) Interpreter to use
either for results,
evaluation, or report-
ing error messages.
ClientData clientData(in) The native description
of the path object to
create.
Tcl_Obj *firstPtr(in) The first of two path
objects to compare.
The object may be con-
verted to path type.
Tcl_Obj *secondPtr(in) The second of two path
objects to compare.
The object may be con-
verted to path type.
Tcl_Obj *listObj (in) The list of path ele-
ments to operate on
with a join operation.
int elements (in) If non-negative, the
number of elements in
the listObj which
should be joined
together. If nega-
tive, then all ele-
ments are joined.
Tcl_Obj **errorPtr(out) In the case of an
error, filled with an
object containing the
name of the file which
caused an error in the
various copy/rename
operations.
Tcl_Obj **objPtrRef(out) Filled with an object
containing the result
of the operation.
Tcl_Obj *result (out) Pre-allocated object
in which to store (by
lappending) the list
of files or directo-
ries which are suc-
cessfully matched in
Tcl_FSMatchInDirec-
tory.
int mode (in) Mask consisting of one
or more of R_OK, W_OK,
X_OK and F_OK. R_OK,
W_OK and X_OK request
checking whether the
file exists and has
read, write and exe-
cute permissions,
respectively. F_OK
just requests checking
for the existence of
the file.
Tcl_StatBuf *statPtr (out) The structure that
contains the result of
a stat or lstat opera-
tion.
CONST char *sym1 (in) Name of a procedure to
look up in the file's
symbol table
CONST char *sym2 (in) Name of a procedure to
look up in the file's
symbol table
Tcl_PackageInitProc **proc1Ptr(out)
Filled with the init
function for this
code.
Tcl_PackageInitProc **proc2Ptr(out)
Filled with the safe-
init function for this
code.
ClientData *clientDataPtr(out)
Filled with the
clientData value to
pass to this code's
unload function when
it is called.
TclfsUnloadFileProc_ **unloadProcPtr(out)
Filled with the func-
tion to use to unload
this piece of code.
utimbuf *tval (in) The access and modifi-
cation times in this
structure are read and
used to set those val-
ues for a given file.
CONST char *modeString(in) Specifies how the file
is to be accessed.
May have any of the
values allowed for the
mode argument to the
Tcl open command.
int permissions(in) POSIX-style permission
flags such as 0644.
If a new file is cre-
ated, these permis-
sions will be set on
the created file.
int *lenPtr (out) If non-NULL, filled
with the number of
elements in the split
path.
Tcl_Obj *basePtr (in) The base path on to
which to join the
given elements. May
be NULL.
int objc (in) The number of elements
in objv.
Tcl_Obj *CONST objv[] (in) The elements to join
to the given base
path.
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DESCRIPTION
There are several reasons for calling the Tcl_FS... func-
tions rather than calling system level functions like
access and stat directly. First, they will work cross-
platform, so an extension which calls them should work
unmodified on Unix, MacOS and Windows. Second, the Win-
dows implementation of some of these functions fixes some
bugs in the system level calls. Third, these function
calls deal with any 'Utf to platform-native' path conver-
sions which may be required (and may cache the results of
such conversions for greater efficiency on subsequent
calls). Fourth, and perhaps most importantly, all of
these functions are 'virtual filesystem aware'. Any vir-
tual filesystem which has been registered (through
Tcl_FSRegister) may reroute file access to alternative
media or access methods. This means that all of these
functions (and therefore the corresponding file, glob,
pwd, cd, open, etc. Tcl commands) may be operate on
'files' which are not native files in the native filesys-
tem. This also means that any Tcl extension which
accesses the filesystem through this API is automatically
'virtual filesystem aware'. Of course, if an extension
accesses the native filesystem directly (through platform-
specific APIs, for example), then Tcl cannot intercept
such calls.
If appropriate vfs's have been registered, the 'files'
may, to give two examples, be remote (e.g. situated on a
remote ftp server) or archived (e.g. lying inside a .zip
archive). Such registered filesystems provide a lookup
table of functions to implement all or some of the func-
tionality listed here. Finally, the Tcl_FSStat and
Tcl_FSLstat calls abstract away from what the 'struct
stat' buffer buffer is actually declared to be, allowing
the same code to be used both on systems with and systems
without support for files larger than 2GB in size.
The Tcl_FS... are objectified and may cache internal rep-
resentations and other path-related strings (e.g. the cur-
rent working directory). One side-effect of this is that
one must not pass in objects with a refCount of zero to
any of these functions. If such calls were handled, they
might result in memory leaks (under some circumstances,
the filesystem code may wish to retain a reference to the
passed in object, and so one must not assume that after
any of these calls return, the object still has a refCount
of zero - it may have been incremented), or in a direct
segfault due to the object being freed part way through
the complex object manipulation required to ensure that
the path is fully normalized and absolute for filesystem
determination. The practical lesson to learn from this is
that Tcl_Obj *path = Tcl_NewStringObj(...) ;
Tcl_FS...(path) ; Tcl_DecrRefCount(path) is wrong, and may
segfault. The 'path' must have its refCount incremented
before passing it in, or decrementing it. For this rea-
son, objects with a refCount of zero are considered not to
be valid filesystem paths and calling any Tcl_FS API with
such an object will result in no action being taken.
Tcl_FSCopyFile attempts to copy the file given by srcPath-
Ptr to the path name given by destPathPtr. If the two
paths given lie in the same filesystem (according to
Tcl_FSGetFileSystemForPath) then that filesystem's 'copy
file' function is called (if it is non-NULL). Otherwise
the function returns -1 and sets Tcl's errno to the
'EXDEV' posix error code (which signifies a 'cross-domain
link').
Tcl_FSCopyDirectory attempts to copy the directory given
by srcPathPtr to the path name given by destPathPtr. If
the two paths given lie in the same filesystem (according
to Tcl_FSGetFileSystemForPath) then that filesystem's
'copy file' function is called (if it is non-NULL). Oth-
erwise the function returns -1 and sets Tcl's errno to the
'EXDEV' posix error code (which signifies a 'cross-domain
link').
Tcl_FSCreateDirectory attempts to create the directory
given by pathPtr by calling the owning filesystem's 'cre-
ate directory' function.
Tcl_FSDeleteFile attempts to delete the file given by
pathPtr by calling the owning filesystem's 'delete file'
function.
Tcl_FSRemoveDirectory attempts to remove the directory
given by pathPtr by calling the owning filesystem's
'remove directory' function.
Tcl_FSRenameFile attempts to rename the file or directory
given by srcPathPtr to the path name given by destPathPtr.
If the two paths given lie in the same filesystem (accord-
ing to Tcl_FSGetFileSystemForPath) then that filesystem's
'rename file' function is called (if it is non-NULL).
Otherwise the function returns -1 and sets Tcl's errno to
the 'EXDEV' posix error code (which signifies a ``cross-
domain link'').
Tcl_FSListVolumes calls each filesystem which has a non-
NULL 'list volumes' function and asks them to return their
list of root volumes. It accumulates the return values in
a list which is returned to the caller (with a refCount of
0).
Tcl_FSEvalFile reads the file given by pathPtr and evalu-
ates its contents as a Tcl script. It returns the same
information as Tcl_EvalObjEx. If the file couldn't be
read then a Tcl error is returned to describe why the file
couldn't be read. The eofchar for files is '\32' (^Z) for
all platforms. If you require a ``^Z'' in code for string
comparison, you can use ``\032'' or ``\u001a'', which will
be safely substituted by the Tcl interpreter into ``^Z''.
Tcl_FSLoadFile dynamically loads a binary code file into
memory and returns the addresses of two procedures within
that file, if they are defined. The appropriate function
for the filesystem to which pathPtr belongs will be
called. If that filesystem does not implement this func-
tion (most virtual filesystems will not, because of OS
limitations in dynamically loading binary code), Tcl will
attempt to copy the file to a temporary directory and load
that temporary file.
Returns a standard Tcl completion code. If an error
occurs, an error message is left in the interp's result.
Tcl_FSMatchInDirectory is used by the globbing code to
search a directory for all files which match a given pat-
tern. The appropriate function for the filesystem to
which pathPtr belongs will be called.
The return value is a standard Tcl result indicating
whether an error occurred in globbing. Error messages are
placed in interp, but good results are placed in the
resultPtr given.
Note that the 'glob' code implements
recursive patterns internally, so this function will only
ever be passed simple patterns, which can be matched using
the logic of 'string match'. To handle recursion, Tcl
will call this function frequently asking only for direc-
tories to be returned.
Tcl_FSLink replaces the library version of readlink(), and
extends it to support the creation of links. The appro-
priate function for the filesystem to which linkNamePtr
belongs will be called.
If the toPtr is NULL, a readlink action is performed. The
result is a Tcl_Obj specifying the contents of the sym-
bolic link given by linkNamePtr, or NULL if the link could
not be read. The result is owned by the caller, which
should call Tcl_DecrRefCount when the result is no longer
needed. If the toPtr is not NULL, Tcl should create a
link of one of the types passed in in the linkAction flag.
This flag is an or'd combination of TCL_CREATE_SYM-
BOLIC_LINK and TCL_CREATE_HARD_LINK. Where a choice
exists (i.e. more than one flag is passed in), the Tcl
convention is to prefer symbolic links. When a link is
successfully created, the return value should be toPtr
(which is therefore already owned by the caller). If
unsuccessful, NULL should be returned.
Tcl_FSLstat fills the stat structure statPtr with informa-
tion about the specified file. You do not need any access
rights to the file to get this information but you need
search rights to all directories named in the path leading
to the file. The stat structure includes info regarding
device, inode (always 0 on Windows), privilege mode, nlink
(always 1 on Windows), user id (always 0 on Windows),
group id (always 0 on Windows), rdev (same as device on
Windows), size, last access time, last modification time,
and creation time.
If path exists, Tcl_FSLstat returns 0 and the stat struc-
ture is filled with data. Otherwise, -1 is returned, and
no stat info is given.
Tcl_FSUtime replaces the library version of utime.
For results see 'utime' documentation. If successful, the
function will update the 'atime' and 'mtime' values of the
file given.
Tcl_FSFileAttrsGet implements read access for the hookable
'file attributes' subcommand. The appropriate function
for the filesystem to which pathPtr belongs will be
called.
If the result is TCL_OK, then an object was placed in
objPtrRef, which will only be temporarily valid (unless
Tcl_IncrRefCount is called).
Tcl_FSFileAttrsSet implements write access for the hook-
able 'file attributes' subcommand. The appropriate func-
tion for the filesystem to which pathPtr belongs will be
called.
Tcl_FSFileAttrStrings implements part of the hookable
'file attributes' subcommand. The appropriate function
for the filesystem to which pathPtr belongs will be
called.
The called procedure may either return an array of
strings, or may instead return NULL and place a Tcl list
into the given objPtrRef. Tcl will take that list and
first increment its refCount before using it. On comple-
tion of that use, Tcl will decrement its refCount. Hence
if the list should be disposed of by Tcl when done, it
should have a refCount of zero, and if the list should not
be disposed of, the filesystem should ensure it retains a
refCount on the object.
Tcl_FSAccess checks whether the process would be allowed
to read, write or test for existence of the file (or other
file system object) whose name is pathname. If pathname
is a symbolic link on Unix, then permissions of the file
referred by this symbolic link are tested.
On success (all requested permissions granted), zero is
returned. On error (at least one bit in mode asked for a
permission that is denied, or some other error occurred),
-1 is returned.
Tcl_FSStat fills the stat structure statPtr with informa-
tion about the specified file. You do not need any access
rights to the file to get this information but you need
search rights to all directories named in the path leading
to the file. The stat structure includes info regarding
device, inode (always 0 on Windows), privilege mode, nlink
(always 1 on Windows), user id (always 0 on Windows),
group id (always 0 on Windows), rdev (same as device on
Windows), size, last access time, last modification time,
and creation time.
If path exists, Tcl_FSStat returns 0 and the stat struc-
ture is filled with data. Otherwise, -1 is returned, and
no stat info is given.
Tcl_FSOpenFileChannel opens a file specified by pathPtr
and returns a channel handle that can be used to perform
input and output on the file. This API is modeled after
the fopen procedure of the Unix standard I/O library. The
syntax and meaning of all arguments is similar to those
given in the Tcl open command when opening a file. If an
error occurs while opening the channel, Tcl_FSOpen-
FileChannel returns NULL and records a POSIX error code
that can be retrieved with Tcl_GetErrno. In addition, if
interp is non-NULL, Tcl_FSOpenFileChannel leaves an error
message in interp's result after any error.
The newly created channel is not registered in the sup-
plied interpreter; to register it, use Tcl_RegisterChan-
nel, described below. If one of the standard channels,
stdin, stdout or stderr was previously closed, the act of
creating the new channel also assigns it as a replacement
for the standard channel.
Tcl_FSGetCwd replaces the library version of getcwd().
It returns the Tcl library's current working directory.
This may be different to the native platform's working
directory, in the case for which the cwd is not in the
native filesystem.
The result is a pointer to a Tcl_Obj specifying the cur-
rent directory, or NULL if the current directory could not
be determined. If NULL is returned, an error message is
left in the interp's result. The result
already has its refCount incremented for the caller. When
it is no longer needed, that refCount should be decre-
mented. This is needed for thread-safety purposes, to
allow multiple threads to access this and related func-
tions, while ensuring the results are always valid.
Tcl_FSChdir replaces the library version of chdir(). The
path is normalized and then passed to the filesystem which
claims it. If that filesystem does not implement this
function, Tcl will fallback to a combination of stat and
access to check whether the directory exists and has
appropriate permissions.
For results, see chdir() documentation. If successful, we
keep a record of the successful path in cwdPathPtr for
subsequent calls to getcwd.
Tcl_FSPathSeparator returns the separator character to be
used for most specific element of the path specified by
pathPtr (i.e. the last part of the path).
The separator is returned as a Tcl_Obj containing a string
of length 1. If the path is invalid, NULL is returned.
Tcl_FSJoinPath takes the given Tcl_Obj, which should be a
valid list, and returns the path object given by consider-
ing the first 'elements' elements as valid path segments.
If elements < 0, we use the entire list.
Returns object with refCount of zero, containing the
joined path.
Tcl_FSSplitPath takes the given Tcl_Obj, which should be a
valid path, and returns a Tcl List object containing each
segment of that path as an element.
Returns list object with refCount of zero. If the passed
in lenPtr is non-NULL, we use it to return the number of
elements in the returned list.
Tcl_FSEqualPaths tests whether the two paths given repre-
sent the same filesystem object
It returns 1 if the paths are equal, and 0 if they are
different. If either path is NULL, 0 is always returned.
Tcl_FSGetNormalizedPath this important function attempts
to extract from the given Tcl_Obj a unique normalized path
representation, whose string value can be used as a unique
identifier for the file.
It returns the normalized path object, with refCount of
zero, or NULL if the path was invalid or could otherwise
not be successfully converted. Extraction of absolute,
normalized paths is very efficient (because the filesystem
operates on these representations internally), although
the result when the filesystem contains numerous symbolic
links may not be the most user-friendly version of a path.
Tcl_FSJoinToPath takes the given object, which should usu-
ally be a valid path or NULL, and joins onto it the array
of paths segments given.
Returns object with refCount of zero, containing the
joined path.
Tcl_FSConvertToPathType tries to convert the given Tcl_Obj
to a valid Tcl path type, taking account of the fact that
the cwd may have changed even if this object is already
supposedly of the correct type. The filename may begin
with "~" (to indicate current user's home directory) or
"~" (to indicate any user's home directory).
If the conversion succeeds (i.e. the object is a valid
path in one of the current filesystems), then TCL_OK is
returned. Otherwise TCL_ERROR is returned, and an error
message may be left in the interpreter.
Tcl_FSGetInternalRep extracts the internal representation
of a given path object, in the given filesystem. If the
path object belongs to a different filesystem, we return
NULL. If the internal representation is currently NULL, we
attempt to generate it, by calling the filesystem's
Tcl_FSCreateInternalRepProc.
Returns NULL or a valid internal path representation.
This internal representation is cached, so that repeated
calls to this function will not require additional conver-
sions.
Tcl_FSGetTranslatedPath attempts to extract the translated
path from the given Tcl_Obj.
If the translation succeeds (i.e. the object is a valid
path), then it is returned. Otherwise NULL will be
returned, and an error message may be left in the inter-
preter. A "translated" path is one which contains no "~"
or "~user" sequences (these have been expanded to their
current representation in the filesystem). The object
returned is owned by the caller, which must store it or
call Tcl_DecrRefCount to ensure memory is freed. This
function is of little practical use, and Tcl_FSGetNormal-
izedPath or Tcl_GetNativePath are usually better functions
to use for most purposes.
Tcl_FSGetTranslatedStringPath does the same as Tcl_FSGet-
TranslatedPath, but returns a character string or NULL.
The string returned is dynamically allocated and owned by
the caller, which must store it or call ckfree to ensure
it is freed. Again, Tcl_FSGetNormalizedPath or Tcl_GetNa-
tivePath are usually better functions to use for most pur-
poses.
Tcl_FSNewNativePath performs something like that reverse
of the usual obj->path->nativerep conversions. If some
code retrieves a path in native form (from, e.g. readlink
or a native dialog), and that path is to be used at the
Tcl level, then calling this function is an efficient way
of creating the appropriate path object type.
The resulting object is a pure 'path' object, which will
only receive a Utf-8 string representation if that is
required by some Tcl code.
Tcl_FSGetNativePath is for use by the Win/Unix/MacOS
native filesystems, so that they can easily retrieve the
native (char* or TCHAR*) representation of a path. This
function is a convenience wrapper around Tcl_FSGetInter-
nalRep, and assumes the native representation is string-
based. It may be desirable in the future to have non-
string-based native representations (for example, on
MacOS, a representation using a fileSpec of FSRef struc-
ture would probably be more efficient). On Windows a full
Unicode representation would allow for paths of unlimited
length. Currently the representation is simply a charac-
ter string containing the complete, absolute path in the
native encoding.
The native representation is cached so that repeated calls
to this function will not require additional conversions.
Tcl_FSFileSystemInfo returns a list of two elements. The
first element is the name of the filesystem (e.g. "native"
or "vfs" or "zip" or "prowrap", perhaps), and the second
is the particular type of the given path within that
filesystem (which is filesystem dependent). The second
element may be empty if the filesystem does not provide a
further categorization of files.
A valid list object is returned, unless the path object is
not recognized, when NULL will be returned.
Tcl_FSGetFileSystemForPath returns the a pointer to the
Tcl_Filesystem which accepts this path as valid.
If no filesystem will accept the path, NULL is returned.
Tcl_FSGetPathType determines whether the given path is
relative to the current directory, relative to the current
volume, or absolute.
It returns one of TCL_PATH_ABSOLUTE, TCL_PATH_RELATIVE, or
TCL_PATH_VOLUME_RELATIVE
Tcl_AllocStatBuf allocates a Tcl_StatBuf on the system
heap (which may be deallocated by being passed to ckfree.)
This allows extensions to invoke Tcl_FSStat and Tcl_FSL-
Stat without being dependent on the size of the buffer.
That in turn depends on the flags used to build Tcl.
TCL_FILESYSTEM
A filesystem provides a Tcl_Filesystem structure that con-
tains pointers to functions that implement the various
operations on a filesystem; these operations are invoked
as needed by the generic layer, which generally occurs
through the functions listed above.
The Tcl_Filesystem structures are manipulated using the
following methods.
Tcl_FSRegister takes a pointer to a filesystem structure
and an optional piece of data to associated with that
filesystem. On calling this function, Tcl will attach the
filesystem to the list of known filesystems, and it will
become fully functional immediately. Tcl does not check
if the same filesystem is registered multiple times (and
in general that is not a good thing to do). TCL_OK will
be returned.
Tcl_FSUnregister removes the given filesystem structure
from the list of known filesystems, if it is known, and
returns TCL_OK. If the filesystem is not currently regis-
tered, TCL_ERROR is returned.
Tcl_FSData will return the ClientData associated with the
given filesystem, if that filesystem is registered. Oth-
erwise it will return NULL.
Tcl_FSMountsChanged is used to inform the Tcl's core that
the set of mount points for the given (already registered)
filesystem have changed, and that cached file representa-
tions may therefore no longer be correct.
The Tcl_Filesystem structure contains the following
fields:
typedef struct Tcl_Filesystem {
CONST char *typeName;
int structureLength;
Tcl_FSVersion version;
Tcl_FSPathInFilesystemProc *pathInFilesystemProc;
Tcl_FSDupInternalRepProc *dupInternalRepProc;
Tcl_FSFreeInternalRepProc *freeInternalRepProc;
Tcl_FSInternalToNormalizedProc *internalToNormalizedProc;
Tcl_FSCreateInternalRepProc *createInternalRepProc;
Tcl_FSNormalizePathProc *normalizePathProc;
Tcl_FSFilesystemPathTypeProc *filesystemPathTypeProc;
Tcl_FSFilesystemSeparatorProc *filesystemSeparatorProc;
Tcl_FSStatProc *statProc;
Tcl_FSAccessProc *accessProc;
Tcl_FSOpenFileChannelProc *openFileChannelProc;
Tcl_FSMatchInDirectoryProc *matchInDirectoryProc;
Tcl_FSUtimeProc *utimeProc;
Tcl_FSLinkProc *linkProc;
Tcl_FSListVolumesProc *listVolumesProc;
Tcl_FSFileAttrStringsProc *fileAttrStringsProc;
Tcl_FSFileAttrsGetProc *fileAttrsGetProc;
Tcl_FSFileAttrsSetProc *fileAttrsSetProc;
Tcl_FSCreateDirectoryProc *createDirectoryProc;
Tcl_FSRemoveDirectoryProc *removeDirectoryProc;
Tcl_FSDeleteFileProc *deleteFileProc;
Tcl_FSCopyFileProc *copyFileProc;
Tcl_FSRenameFileProc *renameFileProc;
Tcl_FSCopyDirectoryProc *copyDirectoryProc;
Tcl_FSLstatProc *lstatProc;
Tcl_FSLoadFileProc *loadFileProc;
Tcl_FSGetCwdProc *getCwdProc;
Tcl_FSChdirProc *chdirProc;
} Tcl_Filesystem;
Except for the first three fields in this structure which
contain simple data elements, all entries contain
addresses of functions called by the generic filesystem
layer to perform the complete range of filesystem related
actions.
The many functions in this structure are broken down into
three categories: infrastructure functions (almost all of
which must be implemented), operational functions (which
must be implemented if a complete filesystem is provided),
and efficiency functions (which need only be implemented
if they can be done so efficiently, or if they have side-
effects which are required by the filesystem; Tcl has less
efficient emulations it can fall back on). It is impor-
tant to note that, in the current version of Tcl, most of
these fallbacks are only used to handle commands initiated
in Tcl, not in C. What this means is, that if a 'file
rename' command is issued in Tcl, and the relevant
filesystem(s) do not implement their Tcl_FSRenameFileProc,
Tcl's core will instead fallback on a combination of other
filesystem functions (it will use Tcl_FSCopyFileProc fol-
lowed by Tcl_FSDeleteFileProc, and if Tcl_FSCopyFileProc
is not implemented there is a further fallback). However,
if a Tcl_FSRenameFile command is issued at the C level, no
such fallbacks occur. This is true except for the last
four entries in the filesystem table (lstat, load, getcwd
and chdir) for which fallbacks do in fact occur at the C
level.
As an example, here is the filesystem lookup table used by
the "vfs" extension which allows filesystem actions to be
implemented in Tcl.
static Tcl_Filesystem vfsFilesystem = {
"tclvfs",
sizeof(Tcl_Filesystem),
TCL_FILESYSTEM_VERSION_1,
&VfsPathInFilesystem,
&VfsDupInternalRep,
&VfsFreeInternalRep,
/* No internal to normalized, since we don't create any
* pure 'internal' Tcl_Obj path representations */
NULL,
/* No create native rep function, since we don't use it
* and don't choose to support uses of 'Tcl_FSNewNativePath' */
NULL,
/* Normalize path isn't needed - we assume paths only have
* one representation */
NULL,
&VfsFilesystemPathType,
&VfsFilesystemSeparator,
&VfsStat,
&VfsAccess,
&VfsOpenFileChannel,
&VfsMatchInDirectory,
&VfsUtime,
/* We choose not to support symbolic links inside our vfs's */
NULL,
&VfsListVolumes,
&VfsFileAttrStrings,
&VfsFileAttrsGet,
&VfsFileAttrsSet,
&VfsCreateDirectory,
&VfsRemoveDirectory,
&VfsDeleteFile,
/* No copy file - fallback will occur at Tcl level */
NULL,
/* No rename file - fallback will occur at Tcl level */
NULL,
/* No copy directory - fallback will occur at Tcl level */
NULL,
/* Core will use stat for lstat */
NULL,
/* No load - fallback on core implementation */
NULL,
/* We don't need a getcwd or chdir - fallback on Tcl's versions */
NULL,
NULL
};
Any functions which take path names in Tcl_Obj form take
those names in UTF-8 form. The filesystem infrastructure
API is designed to support efficient, cached conversion of
these UTF-8 paths to other native representations.
TYPENAME
The typeName field contains a null-terminated string that
identifies the type of the filesystem implemented, e.g.
native or zip or vfs.
STRUCTURE LENGTH
The structureLength field is generally implemented as
sizeof(Tcl_Filesystem), and is there to allow easier
binary backwards compatibility if the size of the struc-
ture changes in a future Tcl release.
VERSION
The version field should be set to TCL_FILESYSTEM_VER-
SION_1.
FILESYSTEM INFRASTRUCTURE
These fields contain addresses of functions which are used
to associate a particular filesystem with a file path, and
deal with the internal handling of path representations,
for example copying and freeing such representations.
PATHINFILESYSTEMPROC
The pathInFilesystemProc field contains the address of a
function which is called to determine whether a given path
object belongs to this filesystem or not. Tcl will only
call the rest of the filesystem functions with a path for
which this function has returned TCL_OK. If the path does
not belong, -1 should be returned (the behaviour of Tcl
for any other return value is not defined). If TCL_OK is
returned, then the optional clientDataPtr output parameter
can be used to return an internal (filesystem specific)
representation of the path, which will be cached inside
the path object, and may be retrieved efficiently by the
other filesystem functions. Tcl will simultaneously cache
the fact that this path belongs to this filesystem. Such
caches are invalidated when filesystem structures are
added or removed from Tcl's internal list of known
filesystems.
typedef int Tcl_FSPathInFilesystemProc(
Tcl_Obj *pathPtr,
ClientData *clientDataPtr);
DUPINTERNALREPPROC
This function makes a copy of a path's internal represen-
tation, and is called when Tcl needs to duplicate a path
object. If NULL, Tcl will simply not copy the internal
representation, which may then need to be regenerated
later.
typedef ClientData Tcl_FSDupInternalRepProc(
ClientData clientData);
FREEINTERNALREPPROC
Free the internal representation. This must be imple-
mented if internal representations need freeing (i.e. if
some memory is allocated when an internal representation
is generated), but may otherwise be NULL.
typedef void Tcl_FSFreeInternalRepProc(
ClientData clientData);
INTERNALTONORMALIZEDPROC
Function to convert internal representation to a normal-
ized path. Only required if the filesystem creates pure
path objects with no string/path representation. The
return value is a Tcl object whose string representation
is the normalized path.
typedef Tcl_Obj* Tcl_FSInternalToNormalizedProc(
ClientData clientData);
CREATEINTERNALREPPROC
Function to take a path object, and calculate an internal
representation for it, and store that native representa-
tion in the object. May be NULL if paths have no internal
representation, or if the Tcl_FSPathInFilesystemProc for
this filesystem always immediately creates an internal
representation for paths it accepts.
typedef ClientData Tcl_FSCreateInternalRepProc(
Tcl_Obj *pathPtr);
NORMALIZEPATHPROC
Function to normalize a path. Should be implemented for
all filesystems which can have multiple string representa-
tions for the same path object. In Tcl, every 'path' must
have a single unique 'normalized' string representation.
Depending on the filesystem, there may be more than one
unnormalized string representation which refers to that
path (e.g. a relative path, a path with different charac-
ter case if the filesystem is case insensitive, a path
contain a reference to a home directory such as '~', a
path containing symbolic links, etc). If the very last
component in the path is a symbolic link, it should not be
converted into the object it points to (but its case or
other aspects should be made unique). All other path com-
ponents should be converted from symbolic links. This one
exception is required to agree with Tcl's semantics with
'file delete', 'file rename', 'file copy' operating on
symbolic links. This function may be called with
'nextCheckpoint' either at the beginning of the path (i.e.
zero), at the end of the path, or at any intermediate file
separator in the path. It will never point to any other
arbitrary position in the path. In the last of the three
valid cases, the implementation can assume that the path
up to and including the file separator is known and nor-
malized.
typedef int Tcl_FSNormalizePathProc(
Tcl_Interp *interp,
Tcl_Obj *pathPtr,
int nextCheckpoint);
FILESYSTEM OPERATIONS
The fields in this section of the structure contain
addresses of functions which are called to carry out the
basic filesystem operations. A filesystem which expects
to be used with the complete standard Tcl command set must
implement all of these. If some of them are not imple-
mented, then certain Tcl commands may fail when operating
on paths within that filesystem. However, in some
instances this may be desirable (for example, a read-only
filesystem should not implement the last four functions,
and a filesystem which does not support symbolic links
need not implement the readlink function, etc. The Tcl
core expects filesystems to behave in this way).
FILESYSTEMPATHTYPEPROC
Function to determine the type of a path in this filesys-
tem. May be NULL, in which case no type information will
be available to users of the filesystem. The 'type' is
used only for informational purposes, and should be
returned as the string representation of the Tcl_Obj which
is returned. A typical return value might be "networked",
"zip" or "ftp". The Tcl_Obj result is owned by the
filesystem and so Tcl will increment the refCount of that
object if it wishes to retain a reference to it.
typedef Tcl_Obj* Tcl_FSFilesystemPathTypeProc(
Tcl_Obj *pathPtr);
FILESYSTEMSEPARATORPROC
Function to return the separator character(s) for this
filesystem. Must be implemented, otherwise the file sepa-
rator command will not function correctly. The usual
return value will be a Tcl_Obj containing the string "/".
typedef Tcl_Obj* Tcl_FSFilesystemSeparatorProc(
Tcl_Obj *pathPtr);
STATPROC
Function to process a Tcl_FSStat() call. Must be imple-
mented for any reasonable filesystem, since many Tcl level
commands depend crucially upon it (e.g. file atime, file
isdirectory, file size, glob).
typedef int Tcl_FSStatProc(
Tcl_Obj *pathPtr,
Tcl_StatBuf *statPtr);
The Tcl_FSStatProc fills the stat structure statPtr with
information about the specified file. You do not need any
access rights to the file to get this information but you
need search rights to all directories named in the path
leading to the file. The stat structure includes info
regarding device, inode (always 0 on Windows), privilege
mode, nlink (always 1 on Windows), user id (always 0 on
Windows), group id (always 0 on Windows), rdev (same as
device on Windows), size, last access time, last modifica-
tion time, and creation time.
If the file represented by pathPtr exists, the Tcl_FSStat-
Proc returns 0 and the stat structure is filled with data.
Otherwise, -1 is returned, and no stat info is given.
ACCESSPROC
Function to process a Tcl_FSAccess() call. Must be imple-
mented for any reasonable filesystem, since many Tcl level
commands depend crucially upon it (e.g. file exists, file
readable).
typedef int Tcl_FSAccessProc(
Tcl_Obj *pathPtr,
int mode);
The Tcl_FSAccessProc checks whether the process would be
allowed to read, write or test for existence of the file
(or other file system object) whose name is pathname. If
pathname is a symbolic link, then permissions of the file
referred by this symbolic link should be tested.
On success (all requested permissions granted), zero is
returned. On error (at least one bit in mode asked for a
permission that is denied, or some other error occurred),
-1 is returned.
OPENFILECHANNELPROC
Function to process a Tcl_FSOpenFileChannel() call. Must
be implemented for any reasonable filesystem, since any
operations which require open or accessing a file's con-
tents will use it (e.g. open, encoding, and many Tk com-
mands).
typedef Tcl_Channel Tcl_FSOpenFileChannelProc(
Tcl_Interp *interp,
Tcl_Obj *pathPtr,
int mode,
int permissions);
The Tcl_FSOpenFileChannelProc opens a file specified by
pathPtr and returns a channel handle that can be used to
perform input and output on the file. This API is modeled
after the fopen procedure of the Unix standard I/O
library. The syntax and meaning of all arguments is simi-
lar to those given in the Tcl open command when opening a
file, where the mode argument is a combination of the
POSIX flags O_RDONLY, O_WRONLY, etc. If an error occurs
while opening the channel, the Tcl_FSOpenFileChannelProc
returns NULL and records a POSIX error code that can be
retrieved with Tcl_GetErrno. In addition, if interp is
non-NULL, the Tcl_FSOpenFileChannelProc leaves an error
message in interp's result after any error.
The newly created channel is not registered in the sup-
plied interpreter; to register it, use Tcl_RegisterChan-
nel. If one of the standard channels, stdin, stdout or
stderr was previously closed, the act of creating the new
channel also assigns it as a replacement for the standard
channel.
MATCHINDIRECTORYPROC
Function to process a Tcl_FSMatchInDirectory() call. If
not implemented, then glob and recursive copy functional-
ity will be lacking in the filesystem (and this may impact
commands like 'encoding names' which use glob functional-
ity internally).
typedef int Tcl_FSMatchInDirectoryProc(
Tcl_Interp* interp,
Tcl_Obj *result,
Tcl_Obj *pathPtr,
CONST char *pattern,
Tcl_GlobTypeData * types);
The function should return all files or directories (or
other filesystem objects) which match the given pattern
and accord with the types specification given. There are
two ways in which this function may be called. If pattern
is NULL, then pathPtr is a full path specification of a
single file or directory which should be checked for exis-
tence and correct type. Otherwise, pathPtr is a direc-
tory, the contents of which the function should search for
files or directories which have the correct type. In
either case, pathPtr can be assumed to be both non-NULL
and non-empty. It is not currently documented whether
pathPtr will have a file separator at its end of not, so
code should be flexible to both possibilities.
The return value is a standard Tcl result indicating
whether an error occurred in the matching process. Error
messages are placed in interp, but on a TCL_OK result, the
interpreter should not be modified, but rather results
should be added to the result object given (which can be
assumed to be a valid Tcl list). The matches added to
result should include any path prefix given in pathPtr
(this usually means they will be absolute path specifica-
tions). Note that if no matches are found, that simply
leads to an empty result --- errors are only signaled for
actual file or filesystem problems which may occur during
the matching process.
UTIMEPROC
Function to process a Tcl_FSUtime() call. Required to
allow setting (not reading) of times with 'file mtime',
'file atime' and the open-r/open-w/fcopy implementation of
'file copy'.
typedef int Tcl_FSUtimeProc(
Tcl_Obj *pathPtr,
struct utimbuf *tval);
The access and modification times of the file specified by
pathPtr should be changed to the values given in the tval
structure.
The return value is a standard Tcl result indicating
whether an error occurred in the process.
LINKPROC
Function to process a Tcl_FSLink() call. Should be imple-
mented only if the filesystem supports links, and may oth-
erwise be NULL.
typedef Tcl_Obj* Tcl_FSLinkProc(
Tcl_Obj *linkNamePtr,
Tcl_Obj *toPtr,
int linkAction);
If toPtr is NULL, the function is being asked to read the
contents of a link. The result is a Tcl_Obj specifying
the contents of the link given by linkNamePtr, or NULL if
the link could not be read. The result is owned by the
caller, which should call Tcl_DecrRefCount when the result
is no longer needed. If toPtr is not NULL, the function
should attempt to create a link. The result in this case
should be toPtr if the link was successful and NULL other-
wise. In this case the result is not owned by the caller.
See the documentation for Tcl_FSLink for the correct
interpretation of the linkAction flags.
LISTVOLUMESPROC
Function to list any filesystem volumes added by this
filesystem. Should be implemented only if the filesystem
adds volumes at the head of the filesystem, so that they
can be returned by 'file volumes'.
typedef Tcl_Obj* Tcl_FSListVolumesProc(void);
The result should be a list of volumes added by this
filesystem, or NULL (or an empty list) if no volumes are
provided. The result object is considered to be owned by
the filesystem (not by Tcl's core), but should be given a
refCount for Tcl. Tcl will use the contents of the list
and then decrement that refCount. This allows filesystems
to choose whether they actually want to retain a 'master
list' of volumes or not (if not, they generate the list on
the fly and pass it to Tcl with a refCount of 1 and then
forget about the list, if yes, then they simply increment
the refCount of their master list and pass it to Tcl which
will copy the contents and then decrement the count back
to where it was).
Therefore, Tcl considers return values from this proc to
be read-only.
FILEATTRSTRINGSPROC
Function to list all attribute strings which are valid for
this filesystem. If not implemented the filesystem will
not support the file attributes command. This allows
arbitrary additional information to be attached to files
in the filesystem. If it is not implemented, there is no
need to implement the get and set methods.
typedef CONST char** Tcl_FSFileAttrStringsProc(
Tcl_Obj *pathPtr,
Tcl_Obj** objPtrRef);
The called function may either return an array of strings,
or may instead return NULL and place a Tcl list into the
given objPtrRef. Tcl will take that list and first incre-
ment its refCount before using it. On completion of that
use, Tcl will decrement its refCount. Hence if the list
should be disposed of by Tcl when done, it should have a
refCount of zero, and if the list should not be disposed
of, the filesystem should ensure it retains a refCount on
the object.
FILEATTRSGETPROC
Function to process a Tcl_FSFileAttrsGet() call, used by
'file attributes'.
typedef int Tcl_FSFileAttrsGetProc(
Tcl_Interp *interp,
int index,
Tcl_Obj *pathPtr,
Tcl_Obj **objPtrRef);
Returns a standard Tcl return code. The attribute value
retrieved, which corresponds to the index'th element in
the list returned by the Tcl_FSFileAttrStringsProc, is a
Tcl_Obj placed in objPtrRef (if TCL_OK was returned) and
is likely to have a refCount of zero. Either way we must
either store it somewhere (e.g. the Tcl result), or
Incr/Decr its refCount to ensure it is properly freed.
FILEATTRSSETPROC
Function to process a Tcl_FSFileAttrsSet() call, used by
'file attributes'. If the filesystem is read-only, there
is no need to implement this.
typedef int Tcl_FSFileAttrsSetProc(
Tcl_Interp *interp,
int index,
Tcl_Obj *pathPtr,
Tcl_Obj *objPtr);
The attribute value of the index'th element in the list
returned by the Tcl_FSFileAttrStringsProc should be set to
the objPtr given.
CREATEDIRECTORYPROC
Function to process a Tcl_FSCreateDirectory() call.
Should be implemented unless the FS is read-only.
typedef int Tcl_FSCreateDirectoryProc(
Tcl_Obj *pathPtr);
The return value is a standard Tcl result indicating
whether an error occurred in the process. If successful,
a new directory should have been added to the filesystem
in the location specified by pathPtr.
REMOVEDIRECTORYPROC
Function to process a 'Tcl_FSRemoveDirectory()' call.
Should be implemented unless the FS is read-only.
typedef int Tcl_FSRemoveDirectoryProc(
Tcl_Obj *pathPtr,
int recursive,
Tcl_Obj **errorPtr);
The return value is a standard Tcl result indicating
whether an error occurred in the process. If successful,
the directory specified by pathPtr should have been
removed from the filesystem. If the recursive flag is
given, then a non-empty directory should be deleted with-
out error. If an error does occur, the name of the file
or directory which caused the error should be placed in
errorPtr.
DELETEFILEPROC
Function to process a Tcl_FSDeleteFile() call. Should be
implemented unless the FS is read-only.
typedef int Tcl_FSDeleteFileProc(
Tcl_Obj *pathPtr);
The return value is a standard Tcl result indicating
whether an error occurred in the process. If successful,
the file specified by pathPtr should have been removed
from the filesystem. Note that, if the filesystem sup-
ports symbolic links, Tcl will always call this function
and not Tcl_FSRemoveDirectoryProc when needed to delete
them (even if they are symbolic links to directories).
FILESYSTEM EFFICIENCY
LSTATPROC
Function to process a Tcl_FSLstat() call. If not imple-
mented, Tcl will attempt to use the statProc defined above
instead. Therefore it need only be implemented if a
filesystem can differentiate between stat and lstat calls.
typedef int Tcl_FSLstatProc(
Tcl_Obj *pathPtr,
Tcl_StatBuf *statPtr);
The behavior of this function is very similar to that of
the Tcl_FSStatProc defined above, except that if it is
applied to a symbolic link, it returns information about
the link, not about the target file.
COPYFILEPROC
Function to process a Tcl_FSCopyFile() call. If not
implemented Tcl will fall back on open-r, open-w and fcopy
as a copying mechanism. Therefore it need only be imple-
mented if the filesystem can perform that action more
efficiently.
typedef int Tcl_FSCopyFileProc(
Tcl_Obj *srcPathPtr,
Tcl_Obj *destPathPtr);
The return value is a standard Tcl result indicating
whether an error occurred in the copying process. Note
that, destPathPtr is the name of the file which should
become the copy of srcPathPtr. It is never the name of a
directory into which srcPathPtr could be copied (i.e. the
function is much simpler than the Tcl level 'file copy'
subcommand). Note that, if the filesystem supports sym-
bolic links, Tcl will always call this function and not
Tcl_FSCopyDirectoryProc when needed to copy them (even if
they are symbolic links to directories).
RENAMEFILEPROC
Function to process a Tcl_FSRenameFile() call. If not
implemented, Tcl will fall back on a copy and delete mech-
anism. Therefore it need only be implemented if the
filesystem can perform that action more efficiently.
typedef int Tcl_FSRenameFileProc(
Tcl_Obj *srcPathPtr,
Tcl_Obj *destPathPtr);
The return value is a standard Tcl result indicating
whether an error occurred in the renaming process.
COPYDIRECTORYPROC
Function to process a Tcl_FSCopyDirectory() call. If not
implemented, Tcl will fall back on a recursive create-dir,
file copy mechanism. Therefore it need only be imple-
mented if the filesystem can perform that action more
efficiently.
typedef int Tcl_FSCopyDirectoryProc(
Tcl_Obj *srcPathPtr,
Tcl_Obj *destPathPtr,
Tcl_Obj **errorPtr);
The return value is a standard Tcl result indicating
whether an error occurred in the copying process. If an
error does occur, the name of the file or directory which
caused the error should be placed in errorPtr. Note that,
destPathPtr is the name of the directory-name which should
become the mirror-image of srcPathPtr. It is not the name
of a directory into which srcPathPtr should be copied
(i.e. the function is much simpler than the Tcl level
'file copy' subcommand).
LOADFILEPROC
Function to process a Tcl_FSLoadFile() call. If not
implemented, Tcl will fall back on a copy to native-temp
followed by a Tcl_FSLoadFile on that temporary copy.
Therefore it need only be implemented if the filesystem
can load code directly, or it can be implemented simply to
return TCL_ERROR to disable load functionality in this
filesystem entirely.
typedef int Tcl_FSLoadFileProc(
Tcl_Interp * interp,
Tcl_Obj *pathPtr,
Tcl_LoadHandle * handlePtr,
Tcl_FSUnloadFileProc * unloadProcPtr);
Returns a standard Tcl completion code. If an error
occurs, an error message is left in the interp's result.
The function dynamically loads a binary code file into
memory. On a successful load, the handlePtr should be
filled with a token for the dynamically loaded file, and
the unloadProcPtr should be filled in with the address of
a procedure. The procedure will be called with the given
Tcl_LoadHandle as its only parameter when Tcl needs to
unload the file.
UNLOADFILEPROC
Function to unload a previously successfully loaded file.
If load was implemented, then this should also be imple-
mented, if there is any cleanup action required.
typedef void Tcl_FSUnloadFileProc(
Tcl_LoadHandle loadHandle);
GETCWDPROC
Function to process a Tcl_FSGetCwd() call. Most filesys-
tems need not implement this. It will usually only be
called once, if 'getcwd' is called before 'chdir'. May be
NULL.
typedef Tcl_Obj* Tcl_FSGetCwdProc(
Tcl_Interp *interp);
If the filesystem supports a native notion of a current
working directory (which might perhaps change independent
of Tcl), this function should return that cwd as the
result, or NULL if the current directory could not be
determined (e.g. the user does not have appropriate per-
missions on the cwd directory). If NULL is returned, an
error message is left in the interp's result.
CHDIRPROC
Function to process a Tcl_FSChdir() call. If filesystems
do not implement this, it will be emulated by a series of
directory access checks. Otherwise, virtual filesystems
which do implement it need only respond with a positive
return result if the dirName is a valid, accessible direc-
tory in their filesystem. They need not remember the
result, since that will be automatically remembered for
use by GetCwd. Real filesystems should carry out the cor-
rect action (i.e. call the correct system 'chdir' api).
typedef int Tcl_FSChdirProc(
Tcl_Obj *pathPtr);
The Tcl_FSChdirProc changes the applications current work-
ing directory to the value specified in pathPtr. The func-
tion returns -1 on error or 0 on success.
KEYWORDS
stat access filesystem vfs
Tcl 8.4 Filesystem(3)